The identification of objects or other entities is a problem at least as old as history. In modern times the most prevalent solution to the problem is the identification card which serves to establish the identity of the bearer, as well as usually some characteristic, status, or attribute of the bearer. Examples of the above are the employee badge, entry access badges, drivers license, etc. Typically, such identification cards will include a picture of the normal bearer as well as relevant information pertaining to the normal bearer in text form.
While identification cards and the like have generally proven useful for the day to day conduct of affairs nevertheless they are still subject to forgery or tampering, and indeed a moderately sized illegal industry exists for the purpose of providing false identification documents.
Cryptographic techniques have been utilized to improve the security of identification cards and the identification or authentication of documents or other forms of information. For instance, bar codes and other types of codes have been affixed to many different types of identification cards and other types of documents and articles in order to make them more difficult to forge.
One approach to the problem of providing secure identification cards is to include an image of an object to be identified (typically a person's face) on one side of the card and an encrypted signal representing a compressed representation of that image on the other side of the card. To validate the card the encrypted data is decrypted by a verifier and a representation of the print image is generated and displayed for comparison with the printed image on one side of the card.
Another problem with such identification cards and with identification cards generally, is the need to issue and/or verify such cards at multiple locations while still maintaining central accounting and control. A state, for example, may wish to verify expiring drivers licenses before issuing new licenses at numerous motor vehicle offices throughout the state while maintaining central accounting and control of the total number of licenses issued. Also, a third party provider of these services may wish to allow one or more users to issue and/or verify such identification cards at one or more locations and may wish to charge for use of the technology on a per card basis.
Typically, a verifier verifies that a document or identification card is genuine by placing one or more secure decryption keys in the verifier and if the information encoded on the identification card or document with the public key can be unlocked with one or more of the decryption keys it identifies the holder of the document or card as the person described in the encoded information. Each verifier may have different cryptographic key sets to limit the number and types of symbols that may be verified.